The production of vinyl acetate is well known. The preferred method is by way of reacting of acetic acid (I) and ethylene (II) in the presence of oxygen to produce the vinyl acetic monomer (III):
Water and by-products are also produced, notably ethyl acetate. U.S. Pat. No. 6,420,595, entitled “Process Control for Vinyl Acetate Manufacturing” of Hallinan et al., provides an overview of the commercially preferred vapor-phase oxidation process wherein the crude product is fed to an azeotrope column and separated into a product stream and a waste ethyl acetate stream. Further details of this process appear in other patents, such as U.S. Pat. No. 6,410,817 to Colling and U.S. Pat. No. 6,696,596 to Herzog et al.
Alternatively, a liquid phase or mixed phase process can be used as is seen in U.S. Pat. No. 6,620,965 to Adams et al.
U.S. Pat. No. 5,225,388, entitled “Method for Making a Catalyst” of Wunder et al., relates to a process for the preparation of vinyl acetate from ethylene, acetic acid and oxygen or oxygen-containing gases on a catalyst which contains palladium and/or its compounds and, if desired, gold and/or gold compounds and alkali metal compounds as activators and, if desired, additionally cadmium compounds on a support which is composed of SiO2 or a SiO2—Al2O3 mixture having a surface area of 50-250 m2/g, a pore volume of 0.4-1.2 ml/g and a particle size of 4 to 9 mm, which comprises compressing the support particles with the aid of an Li, Mg, Al, Zn or Mn salt of a C2-C20 carboxylic acid or a mixture of such salts as binder.
U.S. Pat. No. 4,897,161, entitled “Separation of Vinyl Acetate from Ethyl Acetate by Extractive Distillation” of Berg et al., describes a process whereby vinyl acetate can be readily separated from ethyl acetate by means of extractive distillation using certain glycols or glycol ethers. Typical effective agents are 2-methyl-2,4-pentanediol, 1,3-butanediol, ethylene glycol methyl ether and diethylene glycol ethyl ether.
U.S. Pat. No. 4,818,347, entitled “Process for the Isolation of Vinyl Acetate” of Roscher et al., relates to a process for the isolation of vinyl acetate from a gas mixture containing vinyl acetate, ethyl acetate, water and carbon dioxide formed in the reaction of ethylene with acetic acid and oxygen in the gas phase over catalysts containing palladium or palladium compounds. The gas mixture leaving the reaction zone is passed into a distillation column and the gas mixture leaving the top thereof is cooled. The gas, which is not condensed during the cooling, is washed with acetic acid in a washing column, an acetic acid solution containing vinyl acetate being obtained. The bottom product from the distillation column is passed to a second distillation column and a side stream containing ethyl acetate is removed from an enrichment zone above the bottom thereof, all or some of the bottom product from the second distillation column, which product chiefly consists of acetic acid, being used for the wash in the washing column. The top vapor of the second distillation column is cooled. A portion of the organic phase of the condensate thereby formed is passed, together with the acetic acid solution obtained as the bottom product in the washing column, into a third distillation column, which may have an intermediate tray. The bottom product of the third distillation column is passed into a fourth distillation column. Pure vinyl acetate is removed at the top of the fourth distillation column.
Another process for the isolation of vinyl acetate by distillation is described in U.S. Pat. No. 5,066,365 entitled “Process for the Isolation of Vinyl Acetate by Distillation” of Roscher et al. This process for the isolation of vinyl acetate involves not combining the bottom product of the recycled gas washings with the water-saturated vinyl acetate but rather introducing it to further multiple distillation columns from the gas mixture formed in the reaction of ethylene with acetic acid and oxygen over catalysts containing palladium or palladium compounds in the gas phase.
A more exotic process is seen in U.S. Pat. No. 5,821,384, entitled “Process for Generating Vinyl Carboxylate Esters” of Zoeller et al., which describes a process for producing a vinyl carboxylate ester from a carbonyl compound and a carboxylic acid anhydride. The process comprises feeding a carboxylic acid anhydride to the middle portion of a reactive distillation column (RDC) while feeding a carbonyl compound to the lower section of the RDC and removing a product comprising the vinyl carboxylate ester. A carboxylic acid co-product corresponding to the anhydride reactant may be removed from the upper section of the RDC with the vinyl carboxylate ester, or from the upper section of the RDC as a separate side draw. Unreacted carbonyl may be removed from the RDC from the top along with the vinyl carboxylate ester or separately removed and recycled to the bottom portion of the RDC. Unreacted anhydride and an alkylidene dicarboxylate may be removed from the base of the RDC and recycled to the middle portion of the RDC. The product vinyl carboxylate may be further purified in one or two additional distillation vessels.
Ethyl acetate may be prepared by a variety of processes, including by way of direct addition of acetic acid with ethylene, or by way of oxidative acetoxylation of ethylene followed by hydrogenation of vinyl acetate or by way of esterification of acetic acid with ethanol. The process of preparing ethyl acetate by direct addition is relatively expensive because of the equipment required for the process. These processes are represented as follows:
Direct (Michael) Addition:
Oxidative Acetoxylation/Hydrogenation:
Esterification:

Other processes include those which use acetaldehyde or ethanol as starting materials.
The synthesis of lower aliphatic esters using heterpolyacids with an aldehyde-free product stream is described in U.S. Pat. No. 6,187,949 entitled “Synthesis of Lower Aliphatic Esters Using Heterpolyacids with an Aldehyde-Free Product Stream” of Froom et al. This invention describes a process for the production of lower aliphatic esters by bringing together in an addition reaction a lower olefin and a saturated, lower aliphatic, mono-carboxylic acid in the vapor phase into contact with a heterpolyacid catalyst. The reactant olefin and acids and any recycled feeds are rendered substantially free of aldehyde impurities prior to being brought into contact with the heterpolyacid catalyst. Acetaldehyde is a catalyst poison and removal of these from the feeds prolongs life and activity of the heteropolyacid catalyst.
U.S. Pat. No. 6,727,380 entitled “Oxidation Process for the Production of Alkenes and Carboxylic Acids” of Ellis et al., U.S. Pat. No. 6,548,697 entitled “Oxidation Process for the Production of Alkenes and Carboxylic Acids” of Ellis et al., and U.S. Pat. No. 6,476,261 entitled “Oxidation Process for the Production of Alkenes and Carboxylic Acids” of Ellis et al., describe a process for the oxidation of a C2 to C4 alkane to produce the corresponding alkene and carboxylic acid and further to integrated processes in which a portion of the produced alkene and carboxylic acid are used as reactants, in a second reaction zone, for the production of alkyl carboxylates.
U.S. Pat. No. 5,936,117, entitled “Carbonylation of Olefins” of Zoeller et al., describes a process for the preparation of aliphatic carbonyl compounds selected from aliphatic carboxylic acids, alkyl esters of aliphatic carboxylic acids and anhydrides of aliphatic carboxylic acids by the carbonylation of olefins in the presence of a catalyst system comprising (1) a primary component selected from at least one Group 6 metal, i.e., chromium, molybdenum, and/or tungsten and (2) a secondary component selected from at least one of certain halides and tertiary and quaternary compounds of a Group 15 element, i.e., nitrogen, phosphorus and/or arsenic. The process can be carried out at moderate carbonylation conditions without the necessity of using an expensive noble metal catalyst, volatile, toxic materials such as nickel tetracarbonyl, formic acid or a formate ester. U.S. Pat. No. 4,405,808 entitled “Process for Preparing Acetic Acid Esters” of Nakajima et al. describes a process for preparing acetic acid esters by reacting acetic acid with an aliphatic lower olefin in vapor phase in the presence of steam and a catalyst selected from aromatic disulfonic acids and their esters. The high activity of the catalyst can be maintained and the product is obtained in a high space time yield by the presence of steam in the reaction. The effect of maintaining the high activity can be further increased by using silica treated with a strong acid as a carrier.
U.S. Pat. No. 4,365,084, entitled “Preparation of Alkyl Carboxylates” of Young, describes a method for the preparation of alkyl carboxylate compounds, and especially α-methylalkyl carboxylate compounds, by reaction of an olefin and a carboxylic acid compound in the presence of a particular type of zeolite catalyst. The zeolites are characterized by a silica to alumina mole ratio of at least 12 and a constraint index of 1 to 12.
In connection with the production of either vinyl acetate or ethyl acetate a large portion of the capital and operating expense is due to purification requirements as is appreciated from the above references, as well as those discussed below.
WO 03/011809 to BP Chemicals, Feb. 2, 2003, describes a process for separating secondary butanol impurity from ethyl acetate by feeding the impure ethyl acetate to a distillation column operating at a pressure of less than 1 bar absolute. This provides (1) a stream comprising ethyl acetate as a major component and (2) a residue or a second stream comprising at least some secondary butanol from ethyl acetate. The process can be applied to purifying ethyl acetate derived from (a) catalytic reaction of ethylene with acetic acid followed by (b) a hydrogenation step. The 2-butanone impurity produced in step (a) is difficult to separate from ethyl acetate, and step (b) converts it to secondary butanol, which can be separated by reduced pressure fractionation.
A process for removing at least one compound selected from acetic acid, acetate esters and aldehydes from a gaseous fraction additionally containing carbon dioxide is described in U.S. Pat. No. 6,663,692 entitled “Process for Purifying Carbon Dioxide-Containing Gas Streams” of de Poitiers et al. The process includes the steps of scrubbing in a scrubber at least part of the gaseous fraction with water and acetic acid to remove the acetic acid, acetate esters and/or aldehydes and removing carbon dioxide from the scrubbed product by absorption in aqueous potassium carbonate. The process may be used to remove acetate esters such as vinyl acetate and ethyl acetate and aldehydes such as acetaldehyde. The process may be employed in the manufacture of vinyl acetate by the reaction of ethylene, acetic acid and an oxygen-containing gas in the presence of a catalyst, or in the catalytic oxidation of (a) ethane and/or (b) ethylene to produce respectively (a) acetic acid and/or ethylene and (b) acetic acid.